Landscape and Urban Planning 44 (1999) 219±226
Sustainability and cities: extending the metabolism model
Peter W.G. Newman1
Professor of City Policy, Murdoch University, Perth, WA 6160, Australia
Received 21 September 1998; accepted 19 February 1999
Abstract
The use of the metabolism concept, expanded to include aspects of livability, is applied to cities to demonstrate the practical
meaning of sustainability. Its application in industrial ecology, urban ecology, urban demonstration projects, business plans
and city comparisons are used to illustrate its potential. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Sustainability; Cities; Metabolism; Livability; Ecosystem; Indicators
1. Introduction
Sustainability has been de®ned through the United
Nations as a global process of development that
minimises environments resources and reduces the
impact on environmental sinks using processes that
simultaneously improve the economy and the quality
of life (UN World Commission on Environment and
Development, 1987). This paper tries to show how a
simple model developed for the Australian State of the
Environment reporting process (Newman et al., 1996)
can be used to give some substance to the application
of sustainability to cities. Data from the Australian
applications and some other case studies are provided
to illustrate how the model works.
2. Application of sustainability to cities
The principles of sustainability can be applied to
cities though the guidance on how this can be done
1
Tel.: +61-8-9360-6913; fax: +61-8-9360-6421
E-mail address: newman@central.murdoch.edu.au
0169-2046/99/$20.00 # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 9 - 2 0 4 6 ( 9 9 ) 0 0 0 0 9 - 2
was not very clear in Agenda 21 or other United
Nations documents (Keating, 1993). It is probably
true to say that the major environmental battles of
the past were fought outside cities but that awareness
of the need to include cities in the global sustainability
agenda, is now universally recognised by environmentalists, governments and industry. The Organisation
for Economic and Cultural Development, the European Community and even the World Bank now
have sustainable cities programs. In 1994 the Global
Forum on Cities and Sustainable Development heard
from 50 cities (Mitlin and Satterthwaite, 1994) and in
1996 the UN held Habitat II, the Second United
Nations Conference on Human Settlements in Istanbul. At the `City Summit' the nations of the world
reported on progress in achieving sustainability in
their cities (UN Centre for Human Settlements, 1996).
Anders (1991), in a global review of the sustainable
cities movement, pointed out:
``The sustainable cities movement seems united in
its perception that the state of the environment
demands action and that cities are an appropriate
forum in which to act''. (p. 17)
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P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
Others such as Yanarella and Levine (1992) suggest
that all sustainability initiatives should be centred
around strategies for designing, redesigning and building sustainable cities. From a global perspective, they
suggest that cities shape the world and that we will
never begin to implement the sustainability process
unless we can relate it to cities.
3. An emerging framework ± the city as an
ecosystem
Throughout this century the city has been conceived
by sociologists, planners and engineers as a ``bazaar, a
seat of political chaos, an infernal machine, a circuit,
and more hopefully, as a community, the human
creation par excellence'' (Brugmann and Hersh
(1991), cited in Roseland (1992)).
One of the strongest themes running through
the literature on urban sustainability is that if we
are to solve our environmental problems we need to
view the city as an ecosystem. As Tjallingii (1993)
puts it:
``The city is (now) conceived as a dynamic and
complex ecosystem. This is not a metaphor, but a
concept of a real city. The social, economic and
cultural systems cannot escape the rules of abiotic
and biotic nature. Guidelines for action will have to be
geared to these rules''. (p. 7)
Like all ecosystems, the city is a system, having
inputs of energy and materials. The main environmental problems (and economic costs) are related
to the growth of these inputs and managing the
increased outputs. By looking at the city as a whole
and by analysing the pathways along which energy
and materials including pollutants move, it is
possible to begin to conceive of management systems
and technologies which allow for the reintegration
of natural processes, increasing the ef®ciency of
resource use, the recycling of wastes as valuable
materials and the conservation of (and even production of) energy.
There may be on-going academic debate about what
constitutes sustainability or an ecosystem approach
(Slocombe, 1993), but what is clear is that many
strategies and programs around the world have begun
to apply such notions both for new development and
redevelopment of existing areas.
4. The extended metabolism model
How does a city de®ne its goals in a way that
enables it to be more sustainable? How do you make
a systematic approach that begins to ful®l the global
and local sustainability agenda? The approach
adopted here is based on the experience of the Human
Settlements Panel in the Australian State of the Environment Reporting process (see Newman et al., 1996)
and on the experience of making a Sustainability Plan
for Philadelphia with the graduate students at the
University of Pennsylvania in 1995 and 1997, as well
as awareness of the World Bank/UN Habitat project on
developing sustainability indicators for cities (World
Bank, 1994).
It is possible to de®ne the goal of sustainability in a
city as the reduction of the city's use of natural
resources and production of wastes while simultaneously improving its livability, so that it can better
®t within the capacities of the local, regional and
global ecosystems.
This is set out in Fig. 1 in a model that is called the
`Extended Metabolism Model of the City'. Metabolism is a biological systems way of looking at the
resource inputs and waste outputs of settlements. This
approach has been developed by a few academics over
the past 30 years, though it has rarely if ever been used
in policy development for city planning (Wolman,
Fig. 1. Extended metabolism model of human settlements.
P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
1965; Boyden et al., 1981; Girardet, 1992). Fig. 1 sets
out how this basic metabolism concept has been
extended to include the dynamics of settlements
and livability in these settlements. It was developed
as the basis of the approach adopted by the Australian
State of the Environment Report (Newman et al.,
1996).
In this model it is possible to specify the physical
and biological basis of the city, as well as its human
basis. The physical and biological processes of converting resources into useful products and wastes is
like the human body's metabolic processes or that of
an ecosystem. They are based on the laws of thermodynamics which show that anything which comes into
a biological system must pass through and that the
amount of waste is therefore dependent on the amount
of resources required. A balance sheet of inputs and
outputs can be created. It also means that we can
manage the wastes produced, but they require energy
221
in order to turn them into anything useful and ultimately all materials will eventually end up as waste.
For example, all carbon products will eventually end
up as CO2 and this is not possible to recycle any
further without enormous energy inputs that in themselves have associated wastes. This is the entropy
factor in metabolism.
What this means, is that the best way to ensure that
there are reductions in impact, is to reduce the
resource inputs. This approach to resource management is implicitly understood by scientists but is not
inherent to an economist's approach which sees only
`open cycles' whenever human ingenuity and technology are applied to natural resources. However, a city is
a physical and biological system. Fig. 2 and Table 1
apply the metabolism concept to Sydney.
The metabolic ¯ows for Sydney in 1970 and 1990
are summarised in Table 1; they show that apart from
a few air quality parameters there has been an increase
Fig. 2. Resource inputs consumed and waste outputs discharged from Sydney, 1990. Source: Newman et al., 1996.
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P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
Table 1
Trends in certain per capita material flows in Sydney, 1970 and
1990; source: Newman et al. (1996)
Population
Sydney 1970
2 790 000
Sydney 1990
3 656 500
Resources inputs
Energy/capita
Domestic
Commercial
Industrial
Transport
88 589 MJ/capita
10%
11%
44%
35%
114 236 MJ/capita
9%
6%
47%
38%
Food/capita (intake)
0.23 tonnes/capita
0.22 tonnes/capita
Water/capita
Domestic
Commercial
Industrial
Agricultural/gardens
Miscellaneous
144 tonnes/capita
36%
5%
20%
24%
15%
180 tonnes/capita
445
9%
13%
16%
18%
Waste outputs
Solid waste/capita
Sewage/capita
Hazardous waste
0.59 tonnes/capita
108 tonnes/capita
0.77 tonnes/capita
128 tonnes/capita
0.04 tonnes/capita
Air waste/capita
CO2
CO
SOx
NOx
HCx
Particulates
7.6 tonnes/capita
7 1 tonnes/capita
204.9 kg/capita
20.5 kg/capita
19.8 kg/capita
63.1 kg/capita
30.6 kg/capita
9.3 tonnes/capita
9.1 tonnes/capita
177.8 kg/capita
4.5 kg/capita
18.1 kg/capita
42.3 kg/capita
4.7 kg/capita
Total waste output
324 million tonnes
505 million tonnes
in per capita resource inputs and waste outputs. The
reduction in hydrocarbons is because they are more
completely burnt in modern automobile engines ± but
this just means that there's more CO2 produced. If CO2
is to be reduced, there needs to be more fundamental
change, such as reducing the need to travel so much
(Newman and Kenworthy, 1999).
The metabolism approach to cities is a purely
biological view, but cities are much more than a
mechanism for processing resources and producing
wastes, they are about creating human opportunity.
Thus Fig. 1 sets out how this basic metabolism concept has been extended to include livability in these
settlements so that the economic and social aspects of
sustainability are integrated with the environmental.
This approach now becomes more of a human ecosystem approach, as suggested by Tjallingii and others
above.
Some typical sustainability indicators for cities
covering metabolic ¯ows and livability are outlined
in Table 2. Livability is about the human requirement
for social amenity, health and well being and includes
both individual and community well-being. Livability
is about the human environment though it can never be
separated from the natural environment. Sustainability
for a city is thus not only the reduction in metabolic
¯ows (resource inputs and waste outputs), it must also
be about increasing human livability (social amenity
and health).
Livability indicators were produced for Sydney and
other Australian settlements for the State of the Environment Report (Newman et al., 1996), but only for 1
year. Further studies can thus determine if these
aspects of sustainability are improving or not.
5. Application of the extended metabolism model
The extended metabolism model can be applied at a
range of levels and to a range of different human
activities, for example:
Industrial areas can examine their inputs of
resources and outputs of waste while measuring
their usual economic parameters and other matters
such as worker health and safety. These data could
then be used to see how mutually useful solutions
could be found such as the recycling of one industry's waste as an important resource substitute for
an adjacent industry. The Kalundborg area of Denmark has made an assessment of this kind (Tibbs,
1992). Ayres and Simonis (1994) have adopted a
similar approach for industrial areas based on
`industrial metabolism'.
Households or neighbourhoods can make an
assessment of their metabolic flows and livability
and together make attempts to do better with both.
Examples of this approach in single developments
are being labeled `urban ecology' (Newman and
Kenworthy, 1999).
Urban demonstration projects can be assessed for
their sustainability using the extended metabolism
model. For example, we were asked to evaluate the
P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
223
Table 2
Annual goals and indicators for sustainable city
1. Energy and air quality
Reduce total energy use per capita
Decrease energy used per dollar of output from industry
Increase proportion of bridging fuels (natural gas) and renewal fuels (wind, solar, biofuels)
Reduce total quantity of air pollutants per capita
Reduce total green house gases (eg Kyoto goals of `demonstrable progress' by 2005 and 5% reductions by 2008±12 from 1990 levels and
then further reductions annually)
Achieve zero days not meeting air quality health standard levels
Reduce fleet average and new vehicle average fuel consumption
Reduce number of vehicles failing emission standards
Reduce number of households complaining of noise reducing
2. Water, materials and waste
Reduce total water use per capita
Achieve zero days not meeting drinking water quality standards
Increase proportion of sewage and industrial waste treated to reusable quality
Decrease amount of sewage and industrial waste discharged to streams or ocean
Reduce consumption of building materials per capita (including declining proportion of old growth timber to plantation timber)
Reduce consumption of paper and packaging per capita
Decrease amount of solid waste (including increasing recycle rates for all components)
Increase amount of organic waste returning to soil and food production
3. Land, green spaces and biodiversity
Preserve agricultural land and bushland at the urban fringe
Increase amount of green space in local or regional parks per capita, particularly in `green belt' around city
Increase amount of urban redevelopment to new development
Increase number of specially zoned transit-oriented locations
Increase density of population and employment in transit-oriented locations
4. Transportation
Reduce car use (vehicle kilometer traveled or vehicle miles traveled) per capita
Increase transit, walk/bike and car pool and decrease sole car use
Reduce average commute to and from work
Increase relative average speed of transit to cars
Increase service kms of transit relative to road provision
Increase cost recovery on transit from fares
Decrease parking spaces per 1000 workers in central business district
Increase length of separated cycleway
5. Livability, human amenity and health
Decrease infant mortality per 1000 births
Increase educational attainment (average years per adult)
Increase local leisure opportunities
Decrease transport fatalities per 100 population
Decrease reported crimes per 1000 population
Decrease deaths from urban violence
Decrease proportion of substandard housing
Increase length of pedestrian-friendly streets (based on specific indicators) in city and sub-centres
Increase proportion of city/suburbs with urban design guidelines to assist communities in redevelopment
Increase proportion of city allowing mixed use, higher density urban villages
Australian Better Cities program which consists of
45 demonstrations of urban innovations. The
approach adopted was to try to see the extent to
which each project was reducing resource inputs,
lowering waste outputs and simultaneously
improving the livability of the urban area (Diver
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P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
Table 3
Sustainability and construction
The Sydney 2000 Olympics are described as the `Green Olympics' due to the Greenpeace winning design for the Olympic Village. In this
Olympic Village there will be 100% renewable electricity (from roof top photo voltaics and wind power), energy efficient buildings, solar hot
water, no poly vinyl chlorides or rain forest timber, a rail service connection, bicycle/pedestrian oriented layout and water and waste recycling
systems (Bell et al., 1995). Karla Bell and Associates who were closely involved in the design have also designed a Swedish new town,
Hammarby Sjostad, which was part of the failed 2004 Stockholm Olympics bid but which will still be built as a `sprearhead for ecological and
environmentally friendly construction' (City of Stockholm, 1997)
The goals of the new town are a model of reduced metabolic flows:
Energy
100% renewable-based electricity and heating
Energy use to not exceed 60 kwh/m2 in 205 and reducing to 50 kwh/m2 by 2015
Transport
80% commuting by non automobile means
20% less traffic by 2005 and 40% less by 2015
15% vehicles using biofuels by 2005 and 25% by 2015
100% freight vehicles electric or low emission vehicles
Material flows
100% solid waste recycled
20% reduction in waste by 2005, 40% by 2015
Water consumption reduced by 50% in 2005 and 60% by 2105
Sewage used for energy extraction and nutrients for farm soil
Stormwater used locally
Building materials
No PVC or non-recyclable materials to be used
No rain forest timbers to be used
New building materials only 50% of construction by 2005 and only 10% by 2015
No `sick-building' chemicals in carpets and furniture glues
et al., 1996). An urban demonstration project in
Jakarta was evaluated in terms of sustainability
using the extended metabolism model (Arief,
1998).
Cities can even extend this evaluation process to
events like the Olympic Games and all the facilities
and infrastructure they require (see Table 3).
Individual businesses can apply the extended metabolism model and create a sustainability plan. The
first business to make a `sustainability report' is
Interface (Anderson, 1998) which is a large US
company making flooring. They began a process in
1994 after the CEO had read Paul Hawken's `The
Ecology of Commerce' (Hawken, 1994) and chose
to follow a Swedish set of principles called Natural
Step (Greyson, 1995). Their process was similar to
the metabolism model in that it examined resources
(`what we take'), dynamics (`what we make') and
wastes (`what we waste'). It did not specify livability outcomes, though their report stressed that
economic productivity improved as much from
staff morale as from new technology. Four hundred
separate sustainability initiatives were specified in
the firm based on the work of 18 different teams.
City comparisons. By comparing indicators for
resource use, wastes and livability in different
cities, it is possible to locate those cities (or parts
or cities) that have something to contribute to
policy debates on sustainability. Few cities have
done full assessments of their resources, wastes and
livability (Newman and Kenworthy, 1999). New
Zealand cities were assessed using the extended
metabolism model (Parliamentary Commission of
the Environment, 1998) and found that the area
requiring most attention was the growth in automobile dependence. Australian cities were studied
P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
225
Table 4
Australian settlements and substainability Ð based on `State of The Environment, Australia 1996'
1. The larger the cities the more sustainable they are in terms of per capita use of resources (land, energy, water) and production of wastes
(solid, liquid and gaseous) and in terms of livability indicators (income, education, housing, accessibility). The reason for this is the economies
of scale and density which mean that they have more public transport and recycling and are generally more innovative with new technology
(Newman and Kenworthy, 1999)
2. Larger cities are however more likely to reach capacity limits in terms of air sheds and water sheds. For large cities to continue to grow they
will need to be even more innovative if they are to be sustainable
3. In geographic cross section across Australian cities there is an increase in metabolic flows and declines in livability indicators from core to
inner to middle to outer to fringe suburbs. This pattern is related to the different urban development periods and most recently has been related
to re-urbanisation by more wealthy residents and firms. This rapid re-urbanisation of more central areas appears to be related to processes of
economic change in the new Information Age which may be helping cities to become less automobile dependent (Newman and Kenworthy,
1999)
4. Ex-urban and coastal settlements beyond the big cities are the least sustainable of all Australian development; they have large environmental
impacts, high metabolic flows and low invability on all indicators. These areas are heavily automobile dependent and highlight how
sustainability and transportation priorities are totally enmeshed
5. Remote aboriginal settlements have low metabolic flows and low livability (especially in regard to employment and health) but are the
settlements where new small-scale eco-technologies are being trialed.
using this approach and showed the broad trends set
out in Table 4.
Cities can operate this model on many such
levels, but most of all they need to be able to
measure how they are doing overall as a city in
reducing their metabolic flows whilst improving
their human livability. Most cities will be able to
point to a few innovations they are making in
sustainability but until they can bring a full
assessment of these matters together they will
not be addressing the fundamentals of urban
sustainability.
6. Conclusion
This paper has provided examples of how the
extended metabolism model can be used to assess
the sustainability of cities. The simultaneous achievement of reduced resources and wastes whilst improving livability provides a framework for guiding our
cities into the future.
References
Anders, R., 1991. The sustainable cities movement. Working paper
no. 2, Institute for Resources and Security Studies, Cambridge,
MA, USA.
Anderson, R., 1998. Sustainability Report. Interface, New York.
Arief, A., 1998. A sustainability assessment of squatter redevelopment on Jakarta. M. Phil. Thesis, Institute for Science and
Technology Policy, Murdoch University, Perth, WA.
Ayres, R.U., Simonis, U.E., 1994. Industrial Metabolism. United
Nations University Press, Japan.
Bell et al., 1995. Environmental guidelines for Sydney 2000, Sydney
Organising Committee for Olympic Games, Sydney, Australia.
Boyden, S. Millar, S Newcombe, K., O'Neill, B., 1981. The
Ecology of a City and its People. ANU Press, Canberra.
Brugmann, J., Hersh, R., 1991. Cities as ecosystems: opportunities
for local government. ICLEI, Toronto.
City of Stockholm, 1997. An environmental program for
Hommarby Sjortad. City of Stockholm.
Diver, G., Newman, P., Kenworthy, J., 1996. An evaluation of
better cities: environmental component. Department of Environment, Sport and Territories, Canberra.
Girardet, H., 1992. The Gaia Atlas of Cities. Gaia Books, London.
Greyson, J., 1995. The Natural Step 1995 ± A Collection of
Articles. The Natural Step, Sausalito, CA.
Hawken, P., 1994. The Ecology of Commerce: A Declaration of
Sustainability. Harper Business, New York.
Keating, M., 1993, The Earth Summit's Agenda for Change: A
Plain Language version of Agenda and Three Other Rio
Agreements, Center for Our Common Future, Geneva.
Mitlin, D., Satterthwaite, D., 1994. Cities and sustainable
development. Discussion paper for UN Global Forum, 1994,
Manchester, IIED, London.
Newman, P., Kenworthy, J., 1999. Sustainability and Cities:
Overcoming Automobile Dependence. Island Press, Washington, DC.
Newman, P.W.G. et al., 1996. Human settlements. In: Australian
State of the Environment Report, Department of Environment,
Sport and Territories, Canberra.
Parliamentary Commission of the Environment, 1998. The Urban
Environment. Parliamentary Commissioner, Wellington, New
Zealand.
226
P.W.G. Newman / Landscape and Urban Planning 44 (1999) 219±226
Roseland, M., 1992. Towards sustainable communities. Canadian
National Round Table on the Environment and the Economy,
Ottawa.
Slocombe, D.S., 1993. Environmental planning, ecosystem science
and ecosystem approaches for integrating environment and
development. Environ. Manag. 17(3), 289±303.
Tibbs, H.B.C., 1992. Industrial ecology: An agenda for environmental management. Pollution Prevention Review, Spring.
Tjallingii, S.P., 1993. Ecopolis: Strategies for Ecologically Sound
Urban Development. Backhuys Publishers, Leiden.
UN Centre for Human Settlements, 1996. An Urbanising World:
Global Review of Human Settlements 1996. Habitat, Nairobi.
UN World Commission on Environment and Development, 1987.
Our Common Future, Oxford University Press, London.
Wolman, A., 1965. The metabolism of the city. Sci. Am. 213,
179.
World Bank, 1994. World Development Report 1994. Oxford
University Press, New York.
Yanarella, E.J., Levine, R.S., 1992. Does sustainable development
lead to sustainability?. Futures 24(8), 759±774.